History panel + undo in the editor (#49) (#63)

Co-authored-by: Steve Dudenhoeffer <[email protected]>

web/src/lib/history.test.ts

@@ -0,0 +1,115 @@
+import { describe, expect, it } from 'vitest'
+import { describeConflict, describeCounts, describeUndo, totalChanges, type ChangeSet } from './history'
+
+function changeSet(over: Partial<ChangeSet> = {}): ChangeSet {
+  return {
+    id: 1,
+    gardenId: 1,
+    actorId: 1,
+    actorName: 'Steve',
+    source: 'ui',
+    summary: 'Did a thing',
+    counts: [],
+    createdAt: '2026-07-21T00:00:00Z',
+    ...over,
+  }
+}
+
+describe('describeCounts', () => {
+  it('pluralizes per entity and names the operation', () => {
+    const cs = changeSet({
+      counts: [
+        { entityType: 'planting', op: 'create', n: 3 },
+        { entityType: 'object', op: 'update', n: 1 },
+      ],
+    })
+    expect(describeCounts(cs)).toBe('3 plantings added, 1 bed changed')
+  })
+
+  it('says nothing rather than "0 changes"', () => {
+    expect(describeCounts(changeSet())).toBe('')
+    expect(describeCounts(changeSet({ counts: [{ entityType: 'object', op: 'create', n: 0 }] }))).toBe('')
+  })
+})
+
+describe('describeConflict', () => {
+  it('names the entity when it has a name', () => {
+    expect(describeConflict({ entityType: 'object', entityId: 4, reason: 'changed', name: 'North Bed' })).toBe(
+      '“North Bed” was edited since, so it was left alone',
+    )
+  })
+
+  it('falls back to the entity kind when it has no name', () => {
+    expect(describeConflict({ entityType: 'planting', entityId: 9, reason: 'missing' })).toBe(
+      'that planting no longer exists',
+    )
+  })
+})
+
+describe('describeUndo', () => {
+  const target = changeSet({ counts: [{ entityType: 'object', op: 'update', n: 3 }] })
+
+  it('is a plain success when nothing conflicted', () => {
+    const out = describeUndo(target, {
+      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 3 }] }),
+      conflicts: [],
+    })
+    expect(out).toEqual({ tone: 'ok', message: 'Undone.' })
+  })
+
+  // The server answers 200 with a null change set when every revision was
+  // already a no-op — reachable by undoing a creation whose object is gone.
+  // Claiming "Undone." there reports work that didn't happen.
+  it("doesn't claim to have undone a no-op", () => {
+    const out = describeUndo(target, { changeSet: null, conflicts: [] })
+    expect(out.tone).toBe('ok')
+    expect(out.message).toBe('Nothing left to undo — this was already reversed.')
+  })
+
+  // The case the issue was specific about: a partial revert really did change
+  // things, so reporting a bare failure would be a lie about what applied.
+  it('says how much applied and what was skipped', () => {
+    const out = describeUndo(target, {
+      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 2 }] }),
+      conflicts: [{ entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' }],
+    })
+    expect(out.tone).toBe('partial')
+    expect(out.message).toBe('2 of 3 changes undone — “North Bed” was edited since, so it was left alone.')
+  })
+
+  it('is an error when nothing applied at all', () => {
+    const out = describeUndo(target, {
+      changeSet: null,
+      conflicts: [{ entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' }],
+    })
+    expect(out.tone).toBe('error')
+    expect(out.message).toBe('Nothing was undone — “North Bed” was edited since, so it was left alone.')
+  })
+
+  it('lists every conflict, not just the first', () => {
+    const out = describeUndo(target, {
+      changeSet: changeSet({ id: 2, counts: [{ entityType: 'object', op: 'update', n: 1 }] }),
+      conflicts: [
+        { entityType: 'object', entityId: 7, reason: 'changed', name: 'North Bed' },
+        { entityType: 'planting', entityId: 8, reason: 'missing' },
+      ],
+    })
+    expect(out.message).toContain('“North Bed”')
+    expect(out.message).toContain('that planting no longer exists')
+  })
+})
+
+describe('totalChanges', () => {
+  it('sums every tally', () => {
+    expect(
+      totalChanges(
+        changeSet({
+          counts: [
+            { entityType: 'planting', op: 'create', n: 12 },
+            { entityType: 'object', op: 'update', n: 1 },
+          ],
+        }),
+      ),
+    ).toBe(13)
+  })
+})